With respect to producing an azo compound, various methods have long been known, including those by means of oxidation reaction, reduction reaction, substitution reaction, addition reaction, or condensation reaction, and other methods, as described in Shin-jikken Kagaku Koza (Maruzen Co. Ltd.), Vol. 14-III, pp. 1516 to 1534. However, most of the methods that have been employed as industrial preparation methods of azo dye compounds are processes whereby a diazonium salt and a coupling component, such as anilines and phenols, are subjected to an azo coupling reaction, from such points of view as availability of raw materials, cost, and yield. Such methods have the drawbacks that the diazonium salt is at risk of exploding, and further the yield is low in accordance with some kinds of diazonium salts and coupling components. Specifically, it is difficult to prepare a diazonium salt having bonded thereto an electron-attracting group, and eventually the production of such a compound necessitates a reaction under a strongly acidic condition. Consequently, when a diazonium compound has a functional group that is unstable under an acidic condition, the above-mentioned reaction cannot be applied to the compound, so the use of such a method is greatly restricted. In particular, among these diazonium salts, many heterocyclic diazonium salts are unstable, and therefore a widely applicable method for the production of a diazonium compound is not yet known. Further, with respect to a coupling component, it is known in a diazo-coupling method that, when the coupling position is unsubstituted, or is substituted with a special substituent, such as a formyl group and a carboxyl group, a coupling reaction proceeds efficiently, whereas when the coupling position is substituted with a substituent, such as a halogen atom (e.g. a fluorine atom, a chlorine atom, a bromine atom), an aryloxy group, and an acyloxy group, almost no dye is formed.
Further, an alternative method, whereby an azo dye compound is prepared by reacting a sulfonylhydrazine compound with a coupling component in a photographic light-sensitive material, is described in, for example, European Patent Nos. 545491A1 and 565165A1. However, according to this method, only when the coupling position of a coupling component is unsubstituted, or is substituted with a special substituent, such as a formyl group or a carboxyl group, in the same manner as a diazonium salt, does a reaction proceed efficiently. Furthermore, the yield of this method is also low.